1. Field of the Invention
The present invention relates to collector device of a trolley-assisted vehicles, such as dump trucks used for the transportation of ores in large mines, etc. In an area in which low cost electric supply is available and thus the fuel cost is comparatively high, trolley-assisted dump trucks are used for decreasing the transportation cost. Furthermore, in mines, in which contamination of the working pit by the exhaust gas of the dump trucks causes a big problem, the same trolley-assisted dump trucks are used for decreasing the amount of exhaust gas. More especially, cheap main electric supply collected by overhead contact system is utilized for the full load up-hill course starting from the working pit located at bottom to outside of the mine and to the contrary the vehicle engine is used for the no load down-hill returning course. The invention relates particularly to a power collector device of such trolley-assisted dump trucks.
2. Prior Art
A conventional power collector device of such a trolley-assisted vehicle is as shown in FIG. 1a and FIG. 1b and it comprises a pantograph controlling circuit 1. By this pantograph controlling circuit 1, a pantograph operating mechanism 2 is operated. When the pantograph is in the working condition contacting with the contact wire, the vehicle is driven through the contact wire supplied power by a current collector and driving circuit not shown in the drawing.
The pantograph controlling circuit 1 is fed from a vehicle mounted battery 4. This vehicle mounted battery 4 is also used as a power source in a controlling circuit (not shown) for electrically driving the trolley-assisted vehicles, for controlling an ac generator driven by the Diesel engine in the engine mode, and for the supply of low voltage power source to the various equipments.
When a mode changing switch 5 provided on the dashboard of the drivers cabin is thrown to trolley mode side T, a controlling relay or a trolley mode relay (TOR) 6 in the pantograph controlling circuit 1 is energized and by the closure of its relay contact 7, a pantograph controlling electromagnetic valve 8 (PV1 and PV2) is energized. More precisely, a pantograph controlling solenoid 8a is energized and a pantograph controlling valve 8b is actuated thereby. By this, pressurized operative fluid (for instance air) is introduced into a cylinder 10 from an operative fluid source 9, and the pantograph 3 is raised by a link mechanism to contact the overhead contact system. By this operation, trolley mode running is prepared by a driving circuit operated by the collected supply current not shown in the drawing.
When the trolley mode changing switch 5 is thrown into the engine mode E side, the TOR relay 6 is deenergized and by the open relay contact 7, the pantograph controlling electromagnetic valve 8 (solenoid 8a and controlling valve 8b) is deenergized and thus the pressurized fluid in the cylinder is drained and thus the pantograph 3 is brought to down position and is separated from the overhead contact system. At the same time, in the illustrated embodiment shown in FIGS. 1a and 1b, an engine mode instruction is initiated by an engine mode relay (ENG) 11 and engine mode self-running by the Diesel engine (not shown) is prepared.
In this known circuit, however, if the driver or the assistant had forgotton to through the mode changing switch 5 to E side (non-trolley mode) at stopping condition and placing the switch to T side (trolley mode) and thus leaving the pantograph at raised condition to contact the overhead contact system, there is a danger that the driver or the assistant may get an electric shock when leaving the vehicle since the vehicle body potential is insulated from the ground by the tire of the dump trucks and thus there is no assurance that the body potential is kept at ground level.
In a usual trolley bus or a new traffic system using a third rail and alway running in the trolley mode, the vehicle body is connected to the ground potential by an earth shoe such as disclosed in the Japanese Utility Model Publication No. 9721/50 or No. 4906/51 when stopping at home station in order to assure security for passengers.
Whereas in the abovementioned trolley-assisted vehicles, which operate by changing the driving mode, more especially in the trolley-assisted dump trucks, as there is no need to consider such a frequent getting on or off of passengers at certain predetermined stations like the third rail new traffic system or the trolley bus, only a general consideration is given for the getting on or off of the driver or assistant at non-limited locations. Namely the only problem to be taken into account is the occasion of getting on or off of the driver or assistant from the trolley-assisted vehicles at non-limited locations.